cranelift-frontend: Add the FunctionBuilder::insert_block_after method

cranelift/frontend/src/frontend.rs

@@ -228,6 +228,11 @@ impl<'a> FunctionBuilder<'a> {
         block
     }
 
+    /// Insert `block` in the layout *after* the existing block `after`.
+    pub fn insert_block_after(&mut self, block: Block, after: Block) {
+        self.func.layout.insert_block_after(block, after);
+    }
+
     /// After the call to this function, new instructions will be inserted into the designated
     /// block, in the order they are declared. You must declare the types of the Block arguments
     /// you will use here.